Volkswagen has equipped its natural gas models of the Polo TGI and Golf TGI with a third natural gas tank made of specially coated, high-strength steel. The Golf’s tank has a volume of 23 liters and increases the total CNG tank volume to 115 liters, or 17.3 kg respectively, which offers a range of up to 422 kilometers in WLTP.

On the Polo with 1.0 three-cylinder engine (66 kW / 90 PS) the additional tank carries 16.5 liters and extends the natural gas storage to 91.5 liters in total, or 13.8 kg respectively, meaning that the Polo can travel up to 368 kilometers on CNG in WLTP. As a back-up, both models come with a gasoline tank – albeit a much smaller version.

Polo TGI with new tank system.

For improved driving dynamics and efficiency, the Golf TGI comes with a new 1.5 liter four-cylinder engine, which is powerful, efficiency and environmentally friendly. Proof of this comes from its fuel consumption of just 3.6 kg – 3.5 kg natural gas over 100 kilometers, and CO2 emissions of just 98–95 g/km.

The new 1.5-liter TGI engine in the Golf uses the TGI Miller combustion process with a high compression ratio of 12.5:1, to increase efficiency and decrease CO2 emissions.

A turbocharger with variable turbine geometry increases the boost pressure, adding more air into the cylinders. This allows the 1.5-liter TGI engine to accelerate powerfully at any time from low speeds.

Driving in CNG mode produces around 25% fewer CO2 emissions than with gasoline. An even better CO2 balance can be achieved by fueling with biomethane or e-gas. Biomethane is extracted from plant residues; e-gas is produced from surplus green energy (power-to-gas), which are added to the fuels.

Furthermore, natural gas generally combusts with less emissions than gasoline or diesel. The exhaust gas contains significantly less carbon monoxide and NOx, while the fraction of soot or fine particles is minimal.

Comments

It has to be better than an EV in terms of range, preferably by a reasonable margin.
It sounds like they went with the smaller tanks and then had an "oops" moment and squeezed in larger ones.
Expect larger main tanks next year.
At least you should be able to refuel quickly, compared to charging a battery.
+ it should be fairly green if you are using Bio or "green" methane.

You are parroting a red herring created by the oilcos. Most of us who own EVs, charge overnight at home and use charge stations when we are on vacations or on other distance trips, not often. At this point with EVs that have 200 miles of range, many people will not need to charge their EV on the road.
Switching to CNG from gasoline doesn't buy you much but perhaps additional complication. The best move might be to drive your present car and wait for an EV that meets your perceived range needs. Once you drive an EV for a while, you realize how obsolete even the latest internal combustion engines really are.

I drive a 2013 VW Passat with the TGI system, this fuel system was formerly known as Ecofuel. It has 500 km of range on CNG (3 cylinders) and an additional 500 with gasoline. We fill up with locally produced bio methane derived from compost and sewage solids. It is about 40 percent cheaper to run on bio methane than gasoline. These cars are surprisingly inexpensive to purchase secondhand here in Sweden and there is a pretty good network of fueling stations. When using the bio methane the carbon foot print is comparable to that of an electric car charged with solar electricity. This car has been great for us .

FERC is reporting Henry hub NG prices at $4.16/mmBTU this winter. This is equivalent to gasoline at about $0.48/gallon. Even with pipeline, compression and dispensing costs plus profit and taxes NG cars in the USA should be a no-brainer. Shifting demand from petroleum to NG could make the USA energy-independent in just a few years. Why the heck hasn't it happened already?

Range is not a major issue in a bifuel setup because you can use the gasoline tank as backup.
With 422 km of range in a bifuel setup VW might as well have used a monofuel (CNG only) engine. That would improve fuel economy even more and increase CNG range even further. There now are plenty of CNG stations in many US states and other countries around the world. Why drive around with a dangerous liquid fuel in a thin metal tank?

CNG cars are expensive and an extra tank will result in additional cost. Perhaps the competition with EVs becomes more pronounced when the range for EVs has increased during the last years (although EVs are even costlier). Whatever the reason, VW must have assessed that an extra tank would be worth the cost. Has anybody noted if they decreased the size of the gasoline tank to facilitate a third CNG tank?